1. Field of the Invention
The invention relates to the use of inertial drive forces to influence the movement of a body. More specifically, the invention relates to motion of two bodies, one of which is abruptly stopped while the motion of the other is maintained by its own inertia. The two bodies are coupled one to another such that the inertial force of the body, whose motion is maintained, is coupled to the body to be abruptly stopped so as to reduce the tendency of the body so stopped to rebound from the mechanism employed in stopping the body.
2. Prior Art
In many devices, a relatively immovable object is located in the path of a moving object. When the moving object strikes the relatively immovable object, the moving object tends to rebound therefrom. Frequently, it is desired that the moving object be brought to an abrupt halt at the position at which the relatively immovable object is injected into the path of motion of the moving body; that is, the rebound of the moving body from the object interfering with its motion is undesirable. In "Method of Damping Rebound of Print Hammer", U.S. Pat. No. 3,670,647, issued June 20, 1972, to Funk et al., a hammer's rebound upon return to rest position is reduced by causing the hammer to expend energy required to free a relay armature from a magnetic pole face. The force expended in freeing the armature dissipates kinetic energy so that the tendency of the hammer to rebound from its nominal rest position is damped.
In "Shock-Absorbing Means Especially Suitable For Use With Typewheels In Printing Apparatus", U.S. Pat. No. 2,382,668, issued to Salmon, Aug. 14, 1945, a printing telegraph apparatus is disclosed in which the energy of the typewheel is dissipated by a spring-loaded frictional clutch. A detent is then immediately brought into engagement with a detent notch on the typewheel spindle to lock the spindle into position without backlash. It should be noted that where devices such as spring-loaded frictional clutches are employed, the frictional loading of the clutch must be such as to provide a compromise between the frictional loading necessary to damp rebound oscillation and the ability of a shaft to move within the frictional clutch while the clutch driven body is maintained in a fixed position. Increasing the degree of frictional coupling rapidly reduces rebound excursions but simultaneously increases the heat generated at the frictional contact surfaces of clutch and drive shaft. Such heat generation can rapidly deteriorate the effective performance of the frictional clutch.
Resilient couplings, such as spring couplers, are frequently used to damp oscillations. However, as Vischer discloses in his "Telegraphic Printing Mechanism", U.S. Pat. No. 1,979,510, springs are often maintained for the mundane purpose of maintaining two parts capable of relative motion in desired alignment. Vischer discloses a rotatable printing wheel which is keyed to a keyway in a shaft so as to permit a low friction sliding action of the typewheel along the length of the shaft. To maintain the key of the wheel in juxtaposition to a selected side of the shaft's keyway, a spring is used which applies a rotating force to the wheel about the shaft. Thus, departures of the wheel key from contact with the selected side of the keyway is readily corrected by the action of the spring.
Type wheels would appear to be ready subjects for consideration of rebound-resonance damping devices since the speed with which these wheels can be positioned directly affects the speed with which the equipment may be operated. In U.S. Pat. No. 3,970,186 for "Damper For A Composite Print Wheel" issued to Sohl et al. on July 20, 1976, a composite print wheel is illustrated in which elongate arms to which various characters are attached are subject to oscillation when the type wheel is brought to an abrupt stop. An elastomer impregnated fabric ring is disclosed which is adhesively coupled to the character arms of the print wheel to reduce oscillation in these arms when the wheel is abruptly stopped. No disclosure is set forth for assuring the alignment of the type wheel itself after it is stopped. This would appear to be a necessary consideration since the rapid oscillation of the character arms on the type wheel would tend to displace the wheel itself from its selected stopping position.
Other devices having character font wheels which are driven to position and abruptly brought to a stop, are disclosed in U.S. Pat. Nos. 3,901,369, "Electric Indicia Embossing Machine" issued Aug. 26, 1975 to Tsukamoto et al.; 3,726,380 "Card Embossing Apparatus" issued Apr. 10, 1973 to Beers et al.; and 3,753,482, "Automatic Push Button Tape Embossing Machine" issued Aug. 21, 1973 to Brown et al. None of these disclosures teach the use of a rebound-resonance suppression device although there is disclosed means for locking the wheel in position after it has come to rest. It should be here noted that locking devices which come into play while a character font wheel is actively cycling as a result of rebound, may inadvertently lock the character font wheel in a nondesired, intermediate position wherein further processes of the equipment are impeded and may even result in damage to the character font wheel.
While the use of frictional clutches followed by the application of locking or braking devices appears to be quite familiar to those skilled in the art of devices wherein a moving body must be brought to an abrupt halt, little consideration appears to have been given to the use of inertial forces to suppress rebound-resonance. The use of inertial force as a means for damping oscillations and reducing torsional stress and strain in drive shafts is exemplified by U.S. Pat. Nos. 2,383,516 and 2,451,513, both entitled "Oscillation Reducing Device" and issued, respectively, on Aug. 28, 1945 and Oct. 19, 1948. Nelson, in U.S. Pat. No. 1,778,641, for "Vibration Damper" issued Oct. 14, 1930, enlists the cooperation of the inertia of a flywheel and the variable drive coupled through a centrifugal friction clutch to counter-act or damp torsional vibration set up in the crankshaft of an engine having a plurality of cranks.
It is an object of the present invention to provide method and apparatus for utilizing inertial forces to suppress rebound-resonance in a body which is brought to an abrupt stop.
It is a further objective of the invention to apply inertial rebound-resonance suppression to abruptly stop bodies after said bodies have been moving in any one of linear, arcuate, or rotary forms of motion.
It is a secific objective of the invention to provide means and method for achieving inertial rebound-resonance suppression of a character font wheel.